Wheelchair

ABSTRACT

A wheelchair is disclosed that comprises a drive system that includes typically two input members carried for oscillatory movement on a frame of the wheelchair. A transmission is system disposed to mechanically interconnect each input member to a respective main ground-engaging wheel of the wheelchair. The transmission system is configured such that oscillatory movement of the input member causes rotational movement of the wheel, thereby enabling a user of the wheelchair to propel it by applying effort to the input member. Independent movement of the two input members can be used to effect steering control of the wheelchair. The wheelchair preferably also has a braking system to resist movement of the main wheels.

[0001] This invention relates to wheelchairs. Specifically, it hasapplication to wheelchairs that can be employed to provide mobility fora person who is unable, or who has limited ability, to walk.

[0002] The most common design of wheelchair is propelled by a user usinghis or her hands to apply a turning force to rings secured to each oftwo main wheels of the wheelchair. However, it is well-recognised thatthis arrangement is not without its disadvantages. Conventionalwheelchairs convert a user's efforts into motion with relatively lowmechanical efficiency, not least because a user can apply force to thewheel in relatively short and discrete pulses. After time, a user'shands may be damaged by the efforts they are required to make. Theaction that a user must perform is not easy, particularly for thosepeople who have limited use of their hands. Moreover, it is not pleasantfor a user to have to directly handle wheels that are in such closecontact with what is often a dirty environment. These disadvantagesencourage users to adopt wheelchairs that are electrically propelled.However, this deprives the user of physical exercise, which they may beunable to obtain in other ways, and is not available to all people dueto expense.

[0003] An aim of this invention is to provide a wheelchair and a drivesystem for a wheelchair that is more efficient and more amenable to itsuser.

[0004] From a first aspect, this invention provides a wheelchaircomprising a drive system that includes an input member carried foroscillatory movement on a frame of the wheelchair, and a transmissionsystem disposed to mechanically interconnect the input member to aground-engaging wheel carried for rotation on the frame, thetransmission system being configured such that oscillatory movement ofthe input member causes rotational movement of the wheel, therebyenabling a user of the wheelchair to propel it by applying effort to theinput member.

[0005] It has been found that the required oscillatory movement canreadily be applied by a user to the input member to cause drive to beapplied to the wheel over a comparatively large proportion of itsrotation. This can be achieved by a user making contact with the inputmember and without requiring the user to make direct contact with thewheel (or any component directly attached to the wheel).

[0006] A typical wheelchair embodying the invention includes two (ormore) ground-engaging wheels. In such embodiments, there is typicallyprovided a respective transmission system for each of the wheels.Preferably, each transmission system is connected to a respective inputmember, the input members being configured such that they may be movedby a user independently, or at least partially independently, of eachother, whereby a user can selectively cause one or other of the wheelsto be driven. In this way, the user can effect steering control.

[0007] The input member is most typically mounted for oscillatorymovement along a linear path. For example, it may be a substantiallyrectilinear path. The path may be in a direction that has a substantialcomponent in a direction of normal forward motion of the wheelchair. Insuch a configuration, the user operates the input members with afore-and-aft pushing movement. In embodiments that include two inputmembers, they may be disposed for motion along paths that areapproximately symmetrical about a central axis of the wheelchair.

[0008] The transmission system may include a first drive gear that iscaused to be driven by movement of the input member. For example, theinput member may be connected to the first drive gear by a flexibleconnecting element such as a chain or a cable. The first gear may be inmesh with a wheel gear. Drive may be transmitted to the wheel by a wheelgear, in which case the wheel gear and the wheel are typically securedfor rotation together in a first direction. The wheel gear and theground-engaging wheel may be free to rotate with respect to one anotherin a second direction, such that the wheelchair can freewheel in aforward direction. For example, the wheel gear and the wheel may beinterconnected through an overrunning clutch.

[0009] In an advantageously compact arrangement, the transmission systemis incorporated into a hub unit of a ground-engaging wheel.

[0010] The extent to which the ground-engaging wheel turns upon eachmovement of the input member (referred to as the “drive ratio” in thisspecification) can be determined by relative sizes of components of thetransmission system. The drive ratio is selected so as to avoid the needfor the user to move the input member excessively rapidly in order tomake satisfactory progress. At the same time, the drive ratio must besuch as to ensure that the user need not apply excessive force in orderto move the wheelchair. Advantageously, the transmission system isconfigured such that the drive ratio can be selected in order to meetthe requirements of a specific user. The transmission system mayfurthermore be configured such that the drive ratio can be varied by theuser while the wheelchair is in use.

[0011] A wheelchair embodying the invention most advantageously furthercomprises a braking system. The braking system may be incorporated intoa housing in common with the transmission system.

[0012] Advantageously, the drive system may be readily applied andremoved from a wheelchair. In such embodiments, the wheelchair may bepropelled in a conventional manner when the drive system is not appliedto the wheelchair.

[0013] An embodiment of the invention will now be described in detail,by way of example, and with reference to the accompanying drawings, inwhich:

[0014]FIG. 1 is a rear view of a wheelchair embodying the invention;

[0015]FIG. 2 is a part-exploded view similar to that of FIG. 1;

[0016]FIG. 3 shows the wheelchair of FIG. 1 with yoke being part of adrive system removed;

[0017]FIG. 4 is a view similar to that of FIG. 3 with the yoke in place;

[0018]FIG. 5 is a view of a bearing housing of the wheelchair FIG. 1showing its adaption for use in the present invention;

[0019]FIG. 6 is a view similar to that of FIG. 5 with the propulsionsystem of the invention in place;

[0020]FIG. 7 shows the yoke of the wheelchair of FIG. 1;

[0021]FIGS. 8 and 9 show an input member of a drive system of awheelchair of FIG. 1;

[0022]FIG. 10 is an exploded sectional view of a hub containing atransmission system and a brake of the wheelchair of FIG. 1; and

[0023]FIGS. 11 and 12 are more detailed views of component assemblieswithin the hub of FIG. 10.

[0024] With reference first to FIG. 1, a wheelchair being a firstembodiment of the invention is constructed around a frame 10, forexample, of tubular steel, aluminium alloy, carbon fibre, and so forth.A seat is formed of flexible (e.g. fabric) elements 12 carried on theframe.

[0025] Four ground-engaging wheels are carried on the frame 10. Two ofthese are main wheels 14 and two are auxiliary wheels 16. The mainwheels 14 are carried towards the rear of the frame and the auxiliarywheels 16 are carried towards the front. The diameter of each main wheel14 is substantially greater than the diameter of each auxiliary wheel16.

[0026] Each auxiliary wheel 16 has a generally solid construction. Theyare carried for rotation about an axis that is generally horizontal whenthe wheelchair is in use such that the wheel can roll over ground uponwhich the wheelchair is supported. Additionally, they can rotate about agenerally vertical axis, in order that the wheel can turn to accommodatesteering movement.

[0027] Each of the main wheels 14 is of spoked construction comprising ahub 20, and a rim and tyre 22 interconnected by a plurality of spokes24. (This is just one form of construction amongst many possibilities.)The hub 20 is carried for rotation by a bearing 30 that is supported ina bearing housing 32 (this being described in greater detail below). Thebearing 30 is configured such that the two main wheels 14 can rotateabout a common axis that is generally horizontal when the wheelchair isin use, thereby allowing the wheels to roll over ground upon which thewheelchair is supported. Each of the main wheels 14 also carries a ring26 centred upon the axis of rotation, and having a diameter less thanthat of the rim 22. A user sitting in the wheelchair can drive itforward by manual application of force to one or both rings 26.

[0028] Thus far, what has been described is a substantially conventionalwheelchair. The particular construction described does not limit thescope of the invention. As will be appreciated, there are many otherforms of construction that might be used for the frame, the seat and thewheels. It should also be noted that the provision of the rings 26 isnot essential to implementation of the invention.

[0029] In addition to the conventional features described above, thisembodiment includes a drive system that a user can operate to drive thewheelchair forward in addition or in the alternative to the rings 26.

[0030] This propulsion system includes a yoke 40. The yoke 40 is formedas of tubular metal, formed to be generally symmetrical about afore-and-aft axis of the wheelchair. The yoke 40 comprises two armportions 42 interconnected by a bridging portion 44.

[0031] Each arm portion 42 is shaped generally as an inverted ‘L’. At alower end region of each arm portion 42, there is hub housing 48 withinwhich is serves to mount the arm on the frame 10. The arm portion 42extends upwardly from the hub housing .48, and curves forward, such thatan upper region of each arm portion extends to a respective side of theseat. The bridging portion 46 extends transversely between the armportions 42 to the rear of the seat.

[0032] Each arm portion 42, on its upper region, carries an input drivehandle 50 that constitutes an input member of the drive system. Theparticular configuration of the drive handle 50 is selected to be mostappropriate for the abilities of a specific user of the wheelchair. Inthe example illustrated in the figures, the drive handle has wrist andfinger supporting pegs suitable for use by a person that has limitedhand function. A drive handle intended for use by a person that has fullhand function might be configured quite differently.

[0033] Each drive handle 50 is mounted on the respective arm portion 42such that it can slide along it between forward and rearward limits.Within the arm, the drive handle 50 is connected to a drive cable 52,which extends within the arm to the hub housing 48. The drive cable 52is therefore caused to move within the arm as the drive handle 50 ismoved along the arm portion 42.

[0034] A transmission system is disposed within the hub housing 48 toconvert movement of the drive cable 52 to rotational movement of theassociated main wheel 14. The hub and its components are shown in FIGS.10 to 12.

[0035] The transmission system includes an annular drive gear 60 thathas a smooth cylindrical outer surface and a toothed inner surface. Thedrive gear 60 is carried for rotation within the hub housing 48 byrolling element bearings 62, such that the drive gear 60 can slideaxially within the housing to a limited extent. A helical compressiongear spring 63 urges the drive gear 60 in an axial direction towards thewheel gear 70 (as will be described below). A length of the drive cable52 is coiled about the outer surface of the drive gear 60, with an endportion of the cable 52 being secured to the drive gear. A helicaltorsion hub spring 64 is secured towards one of its ends to spring guide66 projecting into the hub housing, and is secured towards its oppositeend to the drive gear 60.

[0036] The transmission system further comprises a wheel gear 70 carriedfor rotation on bearings 72 on a spigot 68 that projects within the hubhousing 48. The wheel gear 70 has external teeth that mesh with theteeth of the drive gear 60. The wheel gear 70 further includes driveformations 74 to be described further below.

[0037] When the drive cable is pulled from its neutral position bymovement of the drive handle 50, it is unwound from the drive gear 60,causing the drive gear 60 to rotate. This, in turn, causes the wheelgear 70 to rotate at a speed greater than the speed of the drive gear60. This also causes the hub spring 64 to be placed into tension. Whenthe drive handle 50 is subsequently released, the drive gear is causedto rotate in the opposite direction by the hub spring 64, causing thecable, once again, to wind onto the drive gear 60. The meshing gearteeth of the drive gear 60 and the wheel gear 70 may be formed helicallyso as to urge the drive gear into engagement with the wheel gear as thecable is unwound.

[0038] A drive body 80 is carried on the main wheel 14. The drive bodycomprises a flange that engages with the spokes of the main wheel 14 inorder that rotation of the drive body causes the wheel 14 to rotate. Thedrive body 80 further comprises a spigot that projects into the hubhousing 48 when the wheel is mounted for use on the hub housing 48. Thespigot has a cylindrical outer surface and an end surface that carriesdrive formations 82 that cooperate with the drive formations of thewheel gear 70. The gear spring 63 ensures that the drive formations ofthe wheel gear 70 engage positively with those of the spigot when thecable is pulled, while allowing them to disengage when the cable isreleased. The drive formations are configured to operate as anoverrunning clutch such that drive is transmitted from the wheel gear 70to the drive body 80 as the drive cable 52 is pulled from the hubhousing 48, while the wheel gear 70 can turn freely as the cable isrewound under the action of the hub spring 64. Thus, repeatedoscillatory movement of the drive handle 50 is converted intounidirectional motion of the main wheel 14. The number of turns made bythe main wheel 14 for each movement of the drive handle 50 (the driveratio) is determined by the length of travel of the drive handle, theouter diameter of the drive gear 70, and the ratio of the number ofteeth of the drive gear 60 and the wheel gear 70.

[0039] Use of a drive that operates through a cable allows for a greaterdegree of flexibility than conventional systems. In particular, theposition of the drive handle 50 can readily be positioned to suit aparticular user. While this example has been described as being foroperation by a user's hands, alternative configurations may be moreappropriate for some users (for example, for operation by a user's leg,foot, elbow, or so forth).

[0040] A brake assembly is disposed within the hub housing 48 to actupon the cylindrical outer surface of the drive body 80. The brakeassembly includes first and second brake shoes 84 each mounted on arespective pivot pin 86 within the hub housing 48. Each brake shoe 84has a friction surface that closely surrounds the spigot of the drivebody 80. An elastic brake operating cord 88 is connected to each of thebrake shoes 84 remote from the pivot pin 86, the cord passing through abrake operating plate 90, the operating plate 90 being slidably mountedwithin the hub housing 48. A brake cable 92 is connected to theoperating plate 90, from which it extends through the yoke to therespective arm portion 42. At the arm portion 42, the brake cable 92 isconnected to a brake operating bar 96 that is slidably mounted on thearm portion 42.

[0041] When a user pushes the drive handle 50 in a direction opposite tothat used to drive the chair forward, it slides to push a rod 94 intoengagement with the braking bar 96, to move the braking bar 96 withinthe arm. The braking bar 96 is connected to the brake cable 92, to pullthe brake cable that in turn pulls upon the brake operating plate 90.The brake cable 92 passes over a pulley 98 whereby it movement is causedto pass down the arm to the hub.

[0042] Through movement of the brake cable 92, the operating plate 90 isdisplaced within the hub housing 48, and this in turn places the brakeoperating cord 88 under tension, so pulling the brake shoes intofrictional braking contact with the spigot of the drive body 80. Thus,movement of the associated main wheel 16, and therefore of thewheelchair, is resisted.

[0043] As shown in FIGS. 5 and 6, a hub unit of a wheelchair may requiremodification to enable a propulsion system to be mounted on it. This isas shown in FIG. 5. In this configuration, the wheelchair will stillfunction completely as a manual wheelchair. When the propulsion systemis installed, the wheelchair can be used as described above. In the caseof a wheelchair equipped with quick release wheels the propulsion systemcan be quickly installed and removed. The position occupied by the hubgear when the propulsion systems is installed is shown as a dotted linein FIG. 6.

[0044] Therefore, the system may be added or removed at the user's will.For instance, about their home, it might be left off, because they willbe travelling only over short distances. For use out of their house, thepropulsion system may be quickly attached to assist more rapid progressover longer distances.

1. A wheelchair comprising a drive system that includes an input membercarried for oscillatory movement on a frame of the wheelchair, and atransmission system disposed to mechanically interconnect the inputmember to a ground-engaging wheel carried for rotation on the frame, thetransmission system being configured such that oscillatory movement ofthe input member causes rotational movement of the wheel, therebyenabling a user of the wheelchair to propel it by applying effort to theinput member.
 2. A wheelchair according to any claim 1 that includes twoground-engaging wheels.
 3. A wheelchair according to claim 2 thatincludes a respective transmission system for each of the wheels.
 4. Awheelchair according to claim 3 in which each transmission system isconnected to a respective input member, the input members beingconfigured such that they may be moved by a user independently of eachother
 5. A wheelchair according to claim 1 in which the input member ismounted for oscillatory movement along a linear path.
 6. A wheelchairaccording to claim 5 in which the path is a substantially rectilinearpath.
 7. A wheelchair according to claim 6 in which the path is in adirection that has a substantial component in a direction of normalforward motion of the wheelchair.
 8. A wheelchair according to claim 7including two input members disposed for motion along paths that areapproximately symmetrical about a cental axis of the wheelchair.
 9. Awheelchair according to claim 1 in which the transmission systemincludes a first drive gear that is caused to be driven by movement ofthe input member.
 10. A wheelchair according to claim 9 in which theinput member is connected to the first drive gear by a flexibleconnecting element.
 11. A wheelchair according to claim 9 in which thefirst gear is in mesh with a wheel gear.
 12. A wheelchair according toclaim 11 in which drive is transmitted to the ground-engaging wheel by awheel gear
 13. A wheelchair according to claim 12 in which the wheelgear and the ground-engaging wheel are secured for rotation together ina first direction.
 14. A wheelchair according to claim 12 in which thewheel gear and the ground-engaging wheel can rotate with respect to oneanother in a second direction.
 15. A wheelchair according to claim 11 inwhich the wheel gear and the wheel are interconnected through anoverrunning clutch.
 16. A wheelchair according to claim 1 in which thetransmission system is incorporated into a hub unit of a ground-engagingwheel.
 17. A wheelchair according to claim 1 in which the transmissionsystem is configured such that the drive ratio, being the extent towhich the ground-engaging wheel turns upon each movement of the inputmember, is configured such that the drive ratio can be selected in orderto meet the requirements of a specific user.
 18. A wheelchair accordingto claim 1 in which the transmission system is configured such that thedrive ratio can be varied by the user while the wheelchair is in use.19. A wheelchair according to claim 1 which further comprises a brakingsystem.
 20. A wheelchair according to claim 19 in which the brakingsystem is incorporated into a housing in common with the transmissionsystem.
 21. A wheelchair according to claim 1 in which the drive systemcan be readily applied and removed from a wheelchair.
 22. A wheelchairaccording to claim 21 in which the wheelchair can be propelled in aconventional manner when the drive system is not applied to thewheelchair.